The phrase originates from military contexts where high standards of appearance are expected.

Military Origin

Often used metaphorically to describe any effort to perfect something, not just cleaning.

Metaphoric Use

Originally, spit might have been used for polishing, but now it's about the effort, not saliva.

Used to describe a casual effort to make something look better, not a professional job.

Suggests a quick, often surface-level enhancement, not a deep or thorough process.

Reflects informal personal care and attention, rather than something done by professionals.